The present invention relates to improvements in exercising devices of the general type disclosed in U.S. Pat. No. 4,830,362 and U.S. Pat. No. 4,708,338 wherein the weight of a user is shifted between two pedals to simulate climbing stairs. A hydraulic cylinder having a needle valve in a line between opposite ends of the cylinder resists movement of pedals disclosed in Pat. No. 4,830,362. Force L required for moving the pedals disclosed in Pat. No. 4,708,338 is resisted by an electrical alternator or generator driven through a series of chains and sprockets for dissipating work done by a user.
Climber type exercising devices are commercially available from several manufacturers which incorporate dual single acting hydraulic or pneumatic cylinders having pistons which reciprocate upon movement of spaced pedals. The spaced pedals are connected by a rope or cable extending around a pulley such that a downward force exerted on one pedal is transmitted through the rope or cable for applying an upward force to elevate the other pedal. Hydraulic or pneumatic cylinders are pivotally connected to slides movable along the length of the pedals for adjusting the point at which each pneumatic cylinder is secured to each pedal to adjust the mechanical advantage and consequently force required to move each pedal. Each single action cylinder is independent of the other and the cable or rope pulls one pedal up when the other is pushed down.
Still another type of climber which is commercially available incorporates two hydraulic cylinders in which the base of one of the cylinders is connected through a hydraulic line to the rod end of the other cylinder such that a downward force on one pedal forces hydraulic fluid into the other cylinder for elevating the other pedal.
Difficulty has been encountered with hydraulic systems in some of the climber exercise devices because hydraulic fluid bypasses piston seals causing the stroke of the pedals to be progressively reduced and requiring the user of the apparatus to stop and readjust the hydraulic system.
Climbing type exercising devices heretofore developed have been unduly complicated and has not been adapted to expeditiously change force required for moving the pedals without manipulation of elaborate structural relationships of the components. Physical conditioning equipment for athletic teams and physical education classes for students often require use of a single piece of equipment by several different users of different body size and strength in a short time interval. Further, during warm-up for exercises, less resistance may be desirable than during a subsequent more strenuous phase of the exercise session.